How the Government Knows that 0.02 Percent of California Isn't in Drought

As of Tuesday, precisely 0.02 percent of the state of California was not experiencing drought. We talked to the team that calculates that number to figure out how they know.

The map above shows a small section of the far southeastern part of California. Keep an eye on that little green blob as you zoom out, and you can see the area it covers — a tiny spur at the border with Arizona, right on the Colorado River.

That's the 0.02 percent of California that's not in drought.

In fact, in that region, it's pretty much business as usual, according to Brandon Owl, an employee of Imperial Date Gardens that The Wire spoke with by phone. Imperial Date Gardens grows (as you might expect) dates in the Bard Valley, which comprises much of that green area. The company uses flood irrigation to water its trees, Owl said, a process in which the date orchards are simply flooded with water that's piped in through the state's heavily-controlled systems of canals. "We do twice a month, sometimes three times a month as the harvest nears," Owl said, and so far this year, that pattern hadn't been affected. Date farmers "prefer a hot dry climate," and the weather in the Bard Valley right now "is nothing too out of the ordinary."

Which suggests that the National Drought Mitigation Center, which provides assessments of drought in each of the fifty states, got it about right. Its map of California right now is mottled heavily with oranges and browns denoting the extent of the drought outside the Bard Valley. Curious how the NDMC drew those lines, The Wire called the Center, located in Lincoln, Nebraska, and spoke with climatologist Brian Fuchs.

"If you're standing on that line, conditions aren't going to be that different" on either side, Fuchs said. It's an estimate, drawn each week after looking at 40 to 50 indicators: "precipitation, river and stream flows, soil moisture" among them. The moisture data comes, in part, from the Natural Resources Conservation Service, part of the Department of Agriculture that operates a series of monitoring sites around the country. There aren't any sites close to the Bard Valley, but, again, that's only one indicator.

"We use a convergence of evidence approach: where are the indicators pointing?," Fuchs explained. Among those indicators are on-the-ground reports from over 400 people that each week respond to draft maps put out by the Center. Those monitors help determine what the map looks like: "They tell us, yes, this looks good, or you need to move this line a little bit." It's somewhat subjective, but works well enough to provide guidance to farmers and policymakers across the country each week.

So why is the Bard Valley in good shape, as opposed to the rest of the state? Part of it is that there was rain in the region earlier in the year. But "the memory of that precipitation is eroding," Fuchs said, so even the Bard Valley is moving toward drought conditions. The map of change over the last week shows the area near Bard Valley moving into deeper drought.

A forecast from the Department of Commerce is even more intimidating. It shows the small part of Arizona and that 0.02 percent of California coded as "drought development likely" between now and June.

Given that the rest of the state is already engulfed in drought and, according to Commerce, will see that drought "persist or intensify," the state could be at 99.99 percent drought — the maximum amount in the Center's index — in short order. Which means that the farmers throughout the state that have seen lower crop yields thanks to the drought will continue to do so. And that Imperial Date Farms, so far unaffected, may not be able to do that third flooding at harvest time.